Current switch fabrics employed in high bandwidth switches e.g. Asynchronous Transfer Mode switches and Synchronous Optical Networking Standards/Synchronous Digital Hierarchy SONET/SDH currently interconnect circuit boards via an electrical back plane. Where signals are required to be switched between circuit boards, an electrical switch fabric is also used, with all data paths routed via the back plane to the witch fabric. In order to increase the bandwidth of such systems, the capacity of the back planes and switch fabrics must be increased, with wider data paths and higher clock frequencies. Pin Counts, high clock frequencies and electromagnetic interference (EMI) make this problematic.
Optical back planes and switch fabrics offer the possibility of an architecture which is essentially independent of the bandwidth requirements placed upon it.
Such optical interconnects are discussed in the literature, e.g. BT Technol J Vol 9 No 4 1991, but all the work in this field has so far employed discrete optical components and the costs of fabricating prior art circuits has so far been prohibitive compared to the cost of the conventional electronic solution.
The present Invention aims to improve on this prior art and to provide optical apparatus for providing the required interconnection which is cost-effective when compared to the known electrical solutions.